What it found in 2009 was a strange ribbon "dancing across the boundary", Nasa said, formed by many more neutral atoms streaming in from outside than in the surrounding areas.

Many theories have been developed, but none have been proven to explain why this ribbon exists.

But now, in a paper published in the Astrophysical Journal, researchers have proposed a theory that it says is similar to boats being "trapped" in a harbour.

It builds on an idea proposed in 2009 that the ribbon exists in a place where neutral hydrogen atoms from the solar wind cross the galactic magnetic field. The idea is that they have electrons stripped away and become charged, just as they cross the magnetic region - forcing them to gyrate around the field lines. When they're fired back to the Sun, they pick up electrons and form the ribbon of neutral atoms.

The new theory adds a process in which the rotation of charged ions creates waves in the magnetic field, which traps them in the ribbon.

"Think of the ribbon as a harbor and the solar wind particles it contains as boats," says Nathan Schwadron, the first author on the paper and scientist at The University of New Hampshire, Durham.

"The boats can be trapped in the harbor if the ocean waves outside it are powerful enough. This is the nature of the new ribbon model. The ribbon is a region where particles, originally from the solar wind, become trapped or retained due to intense waves and vibrations in the magnetic field."

If proven correct, the theory could tell us more about how the galactic magnetic field works and how our Solar System interacts with it.

59 Incredible Space Photos

59 Incredible Space Photos

1

of

59

Dusty Space Cloud

This image shows the Large Magellanic Cloud galaxy in infrared light as seen by the Herschel Space Observatory, a European Space Agency-led mission with important NASA contributions, and NASA's Spitzer Space Telescope. In the instruments' combined data, this nearby dwarf galaxy looks like a fiery, circular explosion. Rather than fire, however, those ribbons are actually giant ripples of dust spanning tens or hundreds of light-years. Significant fields of star formation are noticeable in the center, just left of center and at right. The brightest center-left region is called 30 Doradus, or the Tarantula Nebula, for its appearance in visible light.